14C octanoic acid breath tests correlate with scintigraphy in the critically ill

Full text: Gastric stasis is common in the critically ill and reduces tolerance to nasogastric feeding. Scintigraphic measurement of gastric emptying is rarely used in the critically ill for practical reasons. Breath testing would be a more convenient way of determining gastric emptying. The purpose of this study was to validate 14C octanoic acid breath tests against scintigraphy in ventilated patients. 21 unselected mechanically ventilated patients receiving enteral nutrition via a nasogastric tube (14M, mean age 58yrs) were fed a dual radiolabelled nutrient meal consisting of 100ml Ensure, 74KBq 14C octanoic acid and 20MBq 99Tc sulphur colloid. 12 normal volunteers (9M mean age 38yrs) were also studied to establish normal ranges. Dynamic scintigraphic images were collected with subjects in 20 deg LAO position over 4 hours utilising a GE Starcam 300M mobile gamma camera. Breath samples were collected using the RAH 'Rapid-14' collection methodology at baseline and every 10 -15 minutes for 4 hours. Gastric emptying parameters were calculated and correlated. Normal breath test mean t- = 117min (SD=46). Delayed gastric emptying was seen in some of the critically ill patients, mean t- - 143 mm (SD=86). Strongest correlations were between normals scintigraphic t- (t-s) and breath test t- (t-B), r=0.96 (p<0.005). Correlation in the critically ill between scintigraphic retention at 120min and t-B, r=0.75 (p<0.005) and between t-s and t-B, n=16, r=0.73 (p<0.005). Good correlation is demonstrated between scintigraphic gastric emptying and 14C octanoic acid breath tests in normal subjects and the critically ill. This may be a useful alternative for measurement of gastric emptying in the critically ill. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc